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internal/sm2ec: loong64 p256MulBy2

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Sun Yimin 2025-10-14 14:42:57 +08:00 committed by GitHub
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3 changed files with 171 additions and 73 deletions
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212
internal/sm2ec/p256_asm_loong64.s
View File

@ -15,6 +15,7 @@
#define acc1 R8 #define acc1 R8
#define acc2 R9 #define acc2 R9
#define acc3 R10 #define acc3 R10
#define acc4 R11 #define acc4 R11
#define acc5 R12 #define acc5 R12
#define acc6 R13 #define acc6 R13
@ -24,7 +25,9 @@
#define t1 R16 #define t1 R16
#define t2 R17 #define t2 R17
#define t3 R18 #define t3 R18
#define t4 R19
#define hlp0 R19
#define hlp1 R30
#define x0 R20 #define x0 R20
#define x1 R21 #define x1 R21
@ -35,6 +38,9 @@
#define y2 R27 #define y2 R27
#define y3 R31 #define y3 R31
#define const0 R28
#define const1 R29
DATA p256p<>+0x00(SB)/8, $0xffffffffffffffff DATA p256p<>+0x00(SB)/8, $0xffffffffffffffff
DATA p256p<>+0x08(SB)/8, $0xffffffff00000000 DATA p256p<>+0x08(SB)/8, $0xffffffff00000000
DATA p256p<>+0x10(SB)/8, $0xffffffffffffffff DATA p256p<>+0x10(SB)/8, $0xffffffffffffffff
@ -190,7 +196,7 @@ basic_path:
MOVV (8*0)(y_ptr), t1 MOVV (8*0)(y_ptr), t1
MOVV (8*1)(y_ptr), t2 MOVV (8*1)(y_ptr), t2
MOVV (8*2)(y_ptr), t3 MOVV (8*2)(y_ptr), t3
MOVV (8*3)(y_ptr), t4 MOVV (8*3)(y_ptr), hlp0
// Conditional move // Conditional move
MASKNEZ t0, t1, t1 MASKNEZ t0, t1, t1
@ -205,9 +211,9 @@ basic_path:
MASKEQZ t0, acc2, acc2 MASKEQZ t0, acc2, acc2
OR t3, acc2 OR t3, acc2
MASKNEZ t0, t4, t4 MASKNEZ t0, hlp0, hlp0
MASKEQZ t0, acc3, acc3 MASKEQZ t0, acc3, acc3
OR t4, acc3 OR hlp0, acc3
// Store result // Store result
MOVV acc0, (8*0)(res_ptr) MOVV acc0, (8*0)(res_ptr)
@ -225,7 +231,7 @@ basic_path:
MOVV (8*4)(y_ptr), t1 MOVV (8*4)(y_ptr), t1
MOVV (8*5)(y_ptr), t2 MOVV (8*5)(y_ptr), t2
MOVV (8*6)(y_ptr), t3 MOVV (8*6)(y_ptr), t3
MOVV (8*7)(y_ptr), t4 MOVV (8*7)(y_ptr), hlp0
// Conditional move // Conditional move
MASKNEZ t0, t1, t1 MASKNEZ t0, t1, t1
@ -240,9 +246,9 @@ basic_path:
MASKEQZ t0, acc2, acc2 MASKEQZ t0, acc2, acc2
OR t3, acc2 OR t3, acc2
MASKNEZ t0, t4, t4 MASKNEZ t0, hlp0, hlp0
MASKEQZ t0, acc3, acc3 MASKEQZ t0, acc3, acc3
OR t4, acc3 OR hlp0, acc3
// Store result // Store result
MOVV acc0, (8*4)(res_ptr) MOVV acc0, (8*4)(res_ptr)
@ -260,7 +266,7 @@ basic_path:
MOVV (8*8)(y_ptr), t1 MOVV (8*8)(y_ptr), t1
MOVV (8*9)(y_ptr), t2 MOVV (8*9)(y_ptr), t2
MOVV (8*10)(y_ptr), t3 MOVV (8*10)(y_ptr), t3
MOVV (8*11)(y_ptr), t4 MOVV (8*11)(y_ptr), hlp0
// Conditional move // Conditional move
MASKNEZ t0, t1, t1 MASKNEZ t0, t1, t1
@ -275,9 +281,9 @@ basic_path:
MASKEQZ t0, acc2, acc2 MASKEQZ t0, acc2, acc2
OR t3, acc2 OR t3, acc2
MASKNEZ t0, t4, t4 MASKNEZ t0, hlp0, hlp0
MASKEQZ t0, acc3, acc3 MASKEQZ t0, acc3, acc3
OR t4, acc3 OR hlp0, acc3
// Store result // Store result
MOVV acc0, (8*8)(res_ptr) MOVV acc0, (8*8)(res_ptr)
@ -478,9 +484,9 @@ TEXT ·p256FromMont(SB),NOSPLIT,$0
ADDV acc1, t1, acc5 ADDV acc1, t1, acc5
SGTU acc1, acc5, t3 SGTU acc1, acc5, t3
ADDV t3, acc2, acc6 ADDV t3, acc2, acc6
SGTU acc2, acc6, t4 SGTU acc2, acc6, hlp0
ADDV $1, t2, t2 ADDV $1, t2, t2
ADDV t4, t2, t2 // no carry ADDV hlp0, t2, t2 // no carry
ADDV acc3, t2, acc7 ADDV acc3, t2, acc7
SGTU acc3, acc7, t0 SGTU acc3, acc7, t0
@ -517,6 +523,9 @@ TEXT ·p256Sqr(SB),NOSPLIT,$0
MOVV (8*1)(x_ptr), x1 MOVV (8*1)(x_ptr), x1
MOVV (8*2)(x_ptr), x2 MOVV (8*2)(x_ptr), x2
MOVV (8*3)(x_ptr), x3 MOVV (8*3)(x_ptr), x3
MOVV p256one<>+0x08(SB), const0
ADDV $1, const0, const1
sqrLoop: sqrLoop:
SUBV $1, y_ptr SUBV $1, y_ptr
@ -564,9 +573,9 @@ TEXT sm2P256SqrInternal<>(SB),NOSPLIT,$0
ADDV t1, acc4, acc4 ADDV t1, acc4, acc4
SGTU t1, acc4, t3 SGTU t1, acc4, t3
ADDV t2, acc4, acc4 ADDV t2, acc4, acc4
SGTU t2, acc4, t4 SGTU t2, acc4, hlp0
// ADC $0, acc5 // ADC $0, acc5
OR t3, t4, acc5 OR t3, hlp0, acc5
MULV x1, x3, t0 MULV x1, x3, t0
// ADCS t0, acc4 // ADCS t0, acc4
@ -602,14 +611,14 @@ TEXT sm2P256SqrInternal<>(SB),NOSPLIT,$0
// ALSLV $1, t2, acc4, acc4 // ALSLV $1, t2, acc4, acc4
SLLV $1, acc4, acc4 SLLV $1, acc4, acc4
ADDV t2, acc4, acc4 ADDV t2, acc4, acc4
SRLV $63, acc5, t4 SRLV $63, acc5, hlp0
// ALSLV $1, t3, acc5, acc5 // ALSLV $1, t3, acc5, acc5
SLLV $1, acc5, acc5 SLLV $1, acc5, acc5
ADDV t3, acc5, acc5 ADDV t3, acc5, acc5
SRLV $63, acc6, acc7 SRLV $63, acc6, acc7
// ALSLV $1, t4, acc6, acc6 // ALSLV $1, hlp0, acc6, acc6
SLLV $1, acc6, acc6 SLLV $1, acc6, acc6
ADDV t4, acc6, acc6 ADDV hlp0, acc6, acc6
// Missing products // Missing products
MULV x0, x0, acc0 MULV x0, x0, acc0
@ -793,17 +802,15 @@ TEXT sm2P256SqrInternal<>(SB),NOSPLIT,$0
// Final reduction // Final reduction
ADDV $1, y0, acc4 ADDV $1, y0, acc4
SGTU y0, acc4, t1 SGTU y0, acc4, t1
MOVV p256one<>+0x08(SB), t2 ADDV const0, t1, t1 // no carry
ADDV t2, t1, t1 // no carry
ADDV y1, t1, acc5 ADDV y1, t1, acc5
SGTU y1, acc5, t3 SGTU y1, acc5, t3
ADDV t3, y2, acc6 ADDV t3, y2, acc6
SGTU y2, acc6, t4 SGTU y2, acc6, hlp0
ADDV $1, t2, t2 ADDV hlp0, const1, t2 // no carry
ADDV t4, t2, t2 // no carry
ADDV y3, t2, acc7 ADDV y3, t2, acc7
SGTU y3, acc7, t4 SGTU y3, acc7, hlp0
OR t0, t4, t0 OR t0, hlp0, t0
MASKNEZ t0, y0, y0 MASKNEZ t0, y0, y0
MASKEQZ t0, acc4, acc4 MASKEQZ t0, acc4, acc4
@ -892,8 +899,8 @@ TEXT sm2P256MulInternal<>(SB),NOSPLIT,$0
ADDV t0, acc2, acc2 ADDV t0, acc2, acc2
SGTU t0, acc2, t3 SGTU t0, acc2, t3
ADDV t2, acc2, acc2 ADDV t2, acc2, acc2
SGTU t2, acc2, t4 SGTU t2, acc2, hlp0
OR t3, t4, t2 OR t3, hlp0, t2
MULHVU y1, x1, y0 MULHVU y1, x1, y0
MULV y1, x2, t0 MULV y1, x2, t0
@ -901,8 +908,8 @@ TEXT sm2P256MulInternal<>(SB),NOSPLIT,$0
ADDV t0, acc3, acc3 ADDV t0, acc3, acc3
SGTU t0, acc3, t3 SGTU t0, acc3, t3
ADDV t2, acc3, acc3 ADDV t2, acc3, acc3
SGTU t2, acc3, t4 SGTU t2, acc3, hlp0
OR t3, t4, t2 OR t3, hlp0, t2
MULHVU y1, x2, acc6 MULHVU y1, x2, acc6
MULV y1, x3, t0 MULV y1, x3, t0
@ -910,8 +917,8 @@ TEXT sm2P256MulInternal<>(SB),NOSPLIT,$0
ADDV t0, acc4, acc4 ADDV t0, acc4, acc4
SGTU t0, acc4, t3 SGTU t0, acc4, t3
ADDV t2, acc4, acc4 ADDV t2, acc4, acc4
SGTU t2, acc4, t4 SGTU t2, acc4, hlp0
OR t3, t4, acc5 OR t3, hlp0, acc5
MULHVU y1, x3, acc7 MULHVU y1, x3, acc7
// ADDS t1, acc2 // ADDS t1, acc2
@ -921,14 +928,14 @@ TEXT sm2P256MulInternal<>(SB),NOSPLIT,$0
ADDV y0, acc3, acc3 ADDV y0, acc3, acc3
SGTU y0, acc3, t3 SGTU y0, acc3, t3
ADDV t2, acc3, acc3 ADDV t2, acc3, acc3
SGTU t2, acc3, t4 SGTU t2, acc3, hlp0
OR t3, t4, t2 OR t3, hlp0, t2
// ADCS acc6, acc4 // ADCS acc6, acc4
ADDV acc6, acc4, acc4 ADDV acc6, acc4, acc4
SGTU acc6, acc4, t3 SGTU acc6, acc4, t3
ADDV t2, acc4, acc4 ADDV t2, acc4, acc4
SGTU t2, acc4, t4 SGTU t2, acc4, hlp0
OR t3, t4, t2 OR t3, hlp0, t2
// ADC acc7, acc5 // ADC acc7, acc5
ADDV t2, acc5, acc5 ADDV t2, acc5, acc5
ADDV acc7, acc5, acc5 ADDV acc7, acc5, acc5
@ -976,8 +983,8 @@ TEXT sm2P256MulInternal<>(SB),NOSPLIT,$0
ADDV t0, acc3, acc3 ADDV t0, acc3, acc3
SGTU t0, acc3, t3 SGTU t0, acc3, t3
ADDV t2, acc3, acc3 ADDV t2, acc3, acc3
SGTU t2, acc3, t4 SGTU t2, acc3, hlp0
OR t3, t4, t2 OR t3, hlp0, t2
MULHVU y2, x1, y0 MULHVU y2, x1, y0
MULV y2, x2, t0 MULV y2, x2, t0
@ -985,8 +992,8 @@ TEXT sm2P256MulInternal<>(SB),NOSPLIT,$0
ADDV t0, acc0, acc0 ADDV t0, acc0, acc0
SGTU t0, acc0, t3 SGTU t0, acc0, t3
ADDV t2, acc0, acc0 ADDV t2, acc0, acc0
SGTU t2, acc0, t4 SGTU t2, acc0, hlp0
OR t3, t4, t2 OR t3, hlp0, t2
MULHVU y2, x2, y1 MULHVU y2, x2, y1
MULV y2, x3, t0 MULV y2, x3, t0
@ -994,8 +1001,8 @@ TEXT sm2P256MulInternal<>(SB),NOSPLIT,$0
ADDV t0, acc1, acc1 ADDV t0, acc1, acc1
SGTU t0, acc1, t3 SGTU t0, acc1, t3
ADDV t2, acc1, acc1 ADDV t2, acc1, acc1
SGTU t2, acc1, t4 SGTU t2, acc1, hlp0
OR t3, t4, acc6 OR t3, hlp0, acc6
MULHVU y2, x3, acc7 MULHVU y2, x3, acc7
// ADDS t1, acc3 // ADDS t1, acc3
@ -1005,14 +1012,14 @@ TEXT sm2P256MulInternal<>(SB),NOSPLIT,$0
ADDV y0, acc4, acc4 ADDV y0, acc4, acc4
SGTU y0, acc4, t3 SGTU y0, acc4, t3
ADDV t2, acc4, acc4 ADDV t2, acc4, acc4
SGTU t2, acc4, t4 SGTU t2, acc4, hlp0
OR t3, t4, t2 OR t3, hlp0, t2
// ADCS y1, acc5 // ADCS y1, acc5
ADDV y1, acc5, acc5 ADDV y1, acc5, acc5
SGTU y1, acc5, t3 SGTU y1, acc5, t3
ADDV t2, acc5, acc5 ADDV t2, acc5, acc5
SGTU t2, acc5, t4 SGTU t2, acc5, hlp0
OR t3, t4, t2 OR t3, hlp0, t2
// ADC acc7, acc6 // ADC acc7, acc6
ADDV t2, acc6, acc6 ADDV t2, acc6, acc6
ADDV acc7, acc6, acc6 ADDV acc7, acc6, acc6
@ -1060,8 +1067,8 @@ TEXT sm2P256MulInternal<>(SB),NOSPLIT,$0
ADDV t0, acc4, acc4 ADDV t0, acc4, acc4
SGTU t0, acc4, t3 SGTU t0, acc4, t3
ADDV t2, acc4, acc4 ADDV t2, acc4, acc4
SGTU t2, acc4, t4 SGTU t2, acc4, hlp0
OR t3, t4, t2 OR t3, hlp0, t2
MULHVU y3, x1, y0 MULHVU y3, x1, y0
MULV y3, x2, t0 MULV y3, x2, t0
@ -1069,8 +1076,8 @@ TEXT sm2P256MulInternal<>(SB),NOSPLIT,$0
ADDV t0, acc5, acc5 ADDV t0, acc5, acc5
SGTU t0, acc5, t3 SGTU t0, acc5, t3
ADDV t2, acc5, acc5 ADDV t2, acc5, acc5
SGTU t2, acc5, t4 SGTU t2, acc5, hlp0
OR t3, t4, t2 OR t3, hlp0, t2
MULHVU y3, x2, y1 MULHVU y3, x2, y1
MULV y3, x3, t0 MULV y3, x3, t0
@ -1078,8 +1085,8 @@ TEXT sm2P256MulInternal<>(SB),NOSPLIT,$0
ADDV t0, acc6, acc6 ADDV t0, acc6, acc6
SGTU t0, acc6, t3 SGTU t0, acc6, t3
ADDV t2, acc6, acc6 ADDV t2, acc6, acc6
SGTU t2, acc6, t4 SGTU t2, acc6, hlp0
OR t3, t4, acc7 OR t3, hlp0, acc7
MULHVU y3, x3, t0 MULHVU y3, x3, t0
// ADDS t1, acc4 // ADDS t1, acc4
@ -1089,14 +1096,14 @@ TEXT sm2P256MulInternal<>(SB),NOSPLIT,$0
ADDV y0, acc5, acc5 ADDV y0, acc5, acc5
SGTU y0, acc5, t3 SGTU y0, acc5, t3
ADDV t2, acc5, acc5 ADDV t2, acc5, acc5
SGTU t2, acc5, t4 SGTU t2, acc5, hlp0
OR t3, t4, t2 OR t3, hlp0, t2
// ADCS y1, acc6 // ADCS y1, acc6
ADDV y1, acc6, acc6 ADDV y1, acc6, acc6
SGTU y1, acc6, t3 SGTU y1, acc6, t3
ADDV t2, acc6, acc6 ADDV t2, acc6, acc6
SGTU t2, acc6, t4 SGTU t2, acc6, hlp0
OR t3, t4, t2 OR t3, hlp0, t2
// ADC t0, acc7 // ADC t0, acc7
ADDV t2, acc7, acc7 ADDV t2, acc7, acc7
ADDV t0, acc7, acc7 ADDV t0, acc7, acc7
@ -1154,17 +1161,15 @@ TEXT sm2P256MulInternal<>(SB),NOSPLIT,$0
// Final reduction // Final reduction
ADDV $1, y0, acc4 ADDV $1, y0, acc4
SGTU y0, acc4, t1 SGTU y0, acc4, t1
MOVV p256one<>+0x08(SB), t2 ADDV const0, t1, t1 // no carry
ADDV t2, t1, t1 // no carry
ADDV y1, t1, acc5 ADDV y1, t1, acc5
SGTU y1, acc5, t3 SGTU y1, acc5, t3
ADDV t3, y2, acc6 ADDV t3, y2, acc6
SGTU y2, acc6, t4 SGTU y2, acc6, hlp0
ADDV $1, t2, t2 ADDV hlp0, const1, t2 // no carry
ADDV t4, t2, t2 // no carry
ADDV y3, t2, acc7 ADDV y3, t2, acc7
SGTU y3, acc7, t4 SGTU y3, acc7, hlp0
OR t0, t4, t0 OR t0, hlp0, t0
MASKNEZ t0, y0, y0 MASKNEZ t0, y0, y0
MASKEQZ t0, acc4, acc4 MASKEQZ t0, acc4, acc4
@ -1191,6 +1196,9 @@ TEXT ·p256Mul(SB),NOSPLIT,$0
MOVV in1+8(FP), x_ptr MOVV in1+8(FP), x_ptr
MOVV in2+16(FP), y_ptr MOVV in2+16(FP), y_ptr
MOVV p256one<>+0x08(SB), const0
ADDV $1, const0, const1
MOVV (8*0)(x_ptr), x0 MOVV (8*0)(x_ptr), x0
MOVV (8*1)(x_ptr), x1 MOVV (8*1)(x_ptr), x1
MOVV (8*2)(x_ptr), x2 MOVV (8*2)(x_ptr), x2
@ -1244,15 +1252,15 @@ TEXT ·p256OrdReduce(SB),NOSPLIT,$0
// SBCS x2, acc2 // SBCS x2, acc2
SGTU x2, acc2, t3 SGTU x2, acc2, t3
SUBV x2, acc2, y2 SUBV x2, acc2, y2
SGTU t2, y2, t4 SGTU t2, y2, t0
SUBV t2, y2, y2 SUBV t2, y2, y2
OR t3, t4, t2 OR t3, t0, t2
// SBCS x3, acc3 // SBCS x3, acc3
SGTU x3, acc3, t3 SGTU x3, acc3, t3
SUBV x3, acc3, y3 SUBV x3, acc3, y3
SGTU t2, y3, t4 SGTU t2, y3, t0
SUBV t2, y3, y3 SUBV t2, y3, y3
OR t3, t4, t0 OR t3, t0, t0
MASKNEZ t0, y0, y0 MASKNEZ t0, y0, y0
MASKEQZ t0, acc0, acc0 MASKEQZ t0, acc0, acc0
@ -1303,6 +1311,9 @@ TEXT ·p256Sub(SB),NOSPLIT,$0
MOVV (8*2)(y_ptr), x2 MOVV (8*2)(y_ptr), x2
MOVV (8*3)(y_ptr), x3 MOVV (8*3)(y_ptr), x3
MOVV p256one<>+0x08(SB), const0
ADDV $1, const0, const1
CALL sm2P256Subinternal<>(SB) CALL sm2P256Subinternal<>(SB)
MOVV x0, (8*0)(res_ptr) MOVV x0, (8*0)(res_ptr)
@ -1337,19 +1348,74 @@ TEXT sm2P256Subinternal<>(SB),NOSPLIT,$0
MOVV $1, t1 MOVV $1, t1
MASKEQZ t0, t1, t1 MASKEQZ t0, t1, t1
MOVV p256one<>+0x08(SB), t2 MASKEQZ t0, const0, t3
MASKEQZ t0, t2, t3 MASKEQZ t0, const1, t2
ADDV $1, t2, t2
MASKEQZ t0, t2, t2
SGTU t1, acc0, t4 SGTU t1, acc0, hlp0
SUBV t1, acc0, x0 SUBV t1, acc0, x0
ADDV t4, t3, t3 // no carry ADDV hlp0, t3, t3 // no carry
SGTU t3, acc1, t1 SGTU t3, acc1, t1
SUBV t3, acc1, x1 SUBV t3, acc1, x1
SGTU t1, acc2, t4 SGTU t1, acc2, hlp0
SUBV t1, acc2, x2 SUBV t1, acc2, x2
ADDV t4, t2, t1 // no carry ADDV hlp0, t2, t1 // no carry
SUBV t1, acc3, x3 SUBV t1, acc3, x3
RET RET
/* ---------------------------------------*/
// func p256MulBy2(res, in *p256Element)
TEXT ·p256MulBy2(SB),NOSPLIT,$0
MOVV res+0(FP), res_ptr
MOVV in+8(FP), x_ptr
MOVV (8*0)(x_ptr), y0
MOVV (8*1)(x_ptr), y1
MOVV (8*2)(x_ptr), y2
MOVV (8*3)(x_ptr), y3
MOVV p256one<>+0x08(SB), const0
ADDV $1, const0, const1
p256MulBy2Inline
MOVV x0, (8*0)(res_ptr)
MOVV x1, (8*1)(res_ptr)
MOVV x2, (8*2)(res_ptr)
MOVV x3, (8*3)(res_ptr)
RET
/* ---------------------------------------*/
// (x3, x2, x1, x0) = 2(y3, y2, y1, y0)
#define p256MulBy2Inline \
SRLV $63, y0, t0; \
SLLV $1, y0, x0; \
SRLV $63, y1, t1; \
SLLV $1, y1, x1; \
ADDV t0, x1, x1; \
SRLV $63, y2, t2; \
SLLV $1, y2, x2; \
ADDV t1, x2, x2; \
SRLV $63, y3, t3; \
SLLV $1, y3, x3; \
ADDV t2, x3, x3; \
;\
ADDV $1, x0, acc4; \
SGTU x0, acc4, t0; \
ADDV const0, t0, t0; \
ADDV x1, t0, acc5; \
SGTU x1, acc5, t0; \
ADDV t0, x2, acc6; \
SGTU x2, acc6, t0; \
ADDV const1, t0, t0; \
ADDV x3, t0, acc7; \
SGTU x3, acc7, t0; \
OR t0, t3, t0; \
MASKNEZ t0, x0, x0; \
MASKEQZ t0, acc4, acc4; \
OR acc4, x0; \
MASKNEZ t0, x1, x1; \
MASKEQZ t0, acc5, acc5; \
OR acc5, x1; \
MASKNEZ t0, x2, x2; \
MASKEQZ t0, acc6, acc6; \
OR acc6, x2; \
MASKNEZ t0, x3, x3; \
MASKEQZ t0, acc7, acc7; \
OR acc7, x3

3
internal/sm2ec/sm2p256_asm_loong64.go
View File

@ -56,3 +56,6 @@ func p256OrdReduce(s *p256OrdElement)
//go:noescape //go:noescape
func p256Sub(res, in1, in2 *p256Element) func p256Sub(res, in1, in2 *p256Element)
//go:noescape
func p256MulBy2(res, in *p256Element)

29
internal/sm2ec/sm2p256_asm_loong64_test.go
View File

@ -290,3 +290,32 @@ func TestP256Sub(t *testing.T) {
t.Errorf("in1 < in2: got %v, want %v", res, want) t.Errorf("in1 < in2: got %v, want %v", res, want)
} }
} }
func p256MulBy2Test(t *testing.T, x, p, r *big.Int) {
x1 := new(big.Int).Mul(x, r)
x1 = x1.Mod(x1, p)
y1 := new(big.Int).Mul(big.NewInt(2), r)
y1 = y1.Mod(y1, p)
ax := new(p256Element)
res := new(p256Element)
res2 := new(p256Element)
fromBig(ax, x1)
p256MulBy2(res2, ax)
p256FromMont(res, res2)
resInt := toBigInt(res)
expected := new(big.Int).Mul(x, big.NewInt(2))
expected = expected.Mod(expected, p)
if resInt.Cmp(expected) != 0 {
t.Fatalf("p256MulBy2(%x) = %x, want %x", x, resInt, expected)
}
}
func TestP256MulBy2(t *testing.T) {
p, _ := new(big.Int).SetString("FFFFFFFEFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF00000000FFFFFFFFFFFFFFFF", 16)
r, _ := new(big.Int).SetString("10000000000000000000000000000000000000000000000000000000000000000", 16)
pMinus1 := new(big.Int).Sub(p, big.NewInt(1))
p256MulBy2Test(t, pMinus1, p, r)
p256MulBy2Test(t, big.NewInt(0), p, r)
p256MulBy2Test(t, big.NewInt(1), p, r)
}